Judge John D'Amico began his career of community activism as a leader of a commuter uprising that preserved passenger rail service and led to the formation of New Jersey Transit. His public service began when elected to the Council of the Borough of Oceanport NJ. He then served three terms as a Monmouth County Commissioner. In that office, he focused on environmental issues such as climate change, air pollution, water pollution, over development, and waste mismanagement. He also grappled with homelessness, racism, and nuclear hazards.

D'Amico served in the New Jersey Senate in 1988 and 1989. He sponsored several key bills in the areas of transportation and the environment. In 1992, he was appointed as a Judge of the Superior Court of New Jersey. In 1997, while sitting in the Civil Division in Monmouth County, he developed a new streamlined civil trial procedure called an "Expedited Jury Trial." It is being used statewide and has been emulated in other states.

In 2003, following his retirement from the bench, Judge D'Amico was appointed chair of the New Jersey State Parole Board, where he reformed its policies and procedures, reduced parole revocations and increased programs for tretment of substance abuse and mental illness. He established task forces to work with faith-based entities, non-profit agencies, and community organizations and leaders to promote successful reintegration of offenders in society.

After retirement from the Parole Board, Judge D'Amico became a consultant to the United States Department of Justice, National Institute of Corrections, on parole reform. He is currently chair of the board of trustees of the NY/NJ Baykeeper, a non-profit environmental organization whose mission is to protect, preserve and restore the Hudson/Raritan Estuary. He is also a trustee of the Friends of the Monmouth County Parks. He resides in Oceanport with his wife, Sandra. They have one daughter, Kim Dwyer.